Rabbits are small mammals in the familyLeporidae of the orderLagomorpha (along with the hare and the pika). Oryctolagus cuniculus includes the European rabbit species and its descendants, the over 200 breeds of domestic rabbit. Sylvilagus includes thirteen wild rabbit species, among them the seven types of cottontail. The rabbit is familiar as a wild prey animal and as a domesticated form of livestock and pet throughout much of the world. With its far-reaching effect on ecologies and on cultures, the rabbit (or bunny) has made its way into our daily life—as food, clothing, and companion—and our art, as symbol and muse.

Terminology

Male rabbits are called bucks; females are called does. An older term for an adult rabbit is coney, while rabbit once referred only to the young animals.[1] Another term for a young rabbit is bunny, though this term is often applied informally (especially by children) to rabbits generally, especially domestic ones. More recently, the term kit or kitten has been used to refer to a young rabbit. A young hare is called a leveret; this term is sometimes informally applied to a young rabbit as well.

A group of rabbits is known as a colony or nest (or, occasionally, a warren, though this more commonly refers to where the rabbits live).[2] A group of baby rabbits produced from a single mating is referred to as a litter,[3] and a group of domestic rabbits living together is sometimes called a herd.[4]

Taxonomy

Rabbits and hares were formerly classified in the order Rodentia (rodent) until 1912, when they were moved into a new order, Lagomorpha (which also includes pikas). Below are some of the genera and species of the rabbit.

Differences from hares

Hares are precocial, born relatively mature and mobile with hair and good vision, while rabbits are altricial, born hairless and blind, and requiring closer care. Hares (and cottontail rabbits) live a relatively solitary life in a simple nest above the ground, while most rabbits live in social groups underground in burrows or warrens. Hares are generally larger than rabbits, with ears that are more elongated, and with hind legs that are larger and longer. Hares have not been domesticated, while descendants of the European rabbit are commonly bred as livestock and kept as pets.

As livestock, rabbits are bred for their meat and fur. The earliest breeds were important sources of meat, and so became larger than wild rabbits, but domestic rabbits in modern times range in size from dwarf to giant. Rabbit fur, prized for its softness, can be found in a broad range of coat colors and patterns, as well as lengths. The Angora rabbit breed, for example, was developed for its long, silky fur, which is often hand-spun into yarn. Other domestic rabbit breeds have been developed primarily for the commercial fur trade, including the Rex, which has a short plush coat.

Biology

Evolution

Development of the rabbit heart
(wax models)

Because the rabbit's epiglottis is engaged over the soft palate except when swallowing, the rabbit is an obligate nasal breather. Rabbits have two sets of incisor teeth, one behind the other. This way they can be distinguished from rodents, with which they are often confused.[5]Carl Linnaeus originally grouped rabbits and rodents under the class Glires; later, they were separated as the scientific consensus is that many of their similarities were a result of convergent evolution. However, recent DNA analysis and the discovery of a common ancestor has supported the view that they do share a common lineage, and thus rabbits and rodents are now often referred to together as members of the superorder Glires.[6]

Morphology

Skeleton of the rabbit

The wild rabbit's ear, with its blood vessels close to the surface, is an essential thermoregulator[7] and may be an adaptation to improve hearing in a prey animal that must be alert to many threats. Though the domestic descendants of the European rabbit have been bred, in some cases, for lop ears, such drooping appendages have not been noted in the wild rabbit.[citation needed]

Since speed and agility are a rabbit's main defenses against predators (including the swift fox), rabbits have large hind leg bones and well developed musculature. Though plantigrade at rest, rabbits are on their toes while running, assuming a more digitigrade form. Unlike the paw structure of some other quadrupeds (including dogs and cats), rabbit paws lack pads.[citation needed] Rabbits use their strong nails for digging and (along with their teeth) for defense.[citation needed] Each front foot has four toes plus a dewclaw. Each hind foot has four toes (but no dewclaw).[8]

Most wild rabbits (especially compared to hares) have relatively full, egg-shaped bodies. The soft coat of the wild rabbit is agouti in coloration (or, rarely, melanistic), which aids in camouflage. The tail of the rabbit (with the exception of the cottontail species) is dark on top and white below. Cottontails have white on the top of their tails.[9]

As a result of the position of the eyes in its skull, the rabbit has a field of vision that encompasses nearly 360 degrees, with just a small blind spot at the bridge of the nose.[10]

Digestion

Rabbits are herbivores that feed by grazing on grass, forbs, and leafy weeds. In consequence, their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem via a form of hindgut fermentation. They pass two distinct types of feces: hard droppings and soft black viscous pellets, the latter of which are known as caecotrophs and are immediately eaten (a behaviour known as coprophagy). Rabbits reingest their own droppings (rather than chewing the cud as do cows and numerous other herbivores) to digest their food further and extract sufficient nutrients.[11]

Rabbits graze heavily and rapidly for roughly the first half-hour of a grazing period (usually in the late afternoon), followed by about half an hour of more selective feeding.[citation needed] In this time, the rabbit will also excrete many hard fecal pellets, being waste pellets that will not be reingested.[citation needed] If the environment is relatively non-threatening, the rabbit will remain outdoors for many hours, grazing at intervals.[citation needed] While out of the burrow, the rabbit will occasionally reingest its soft, partially digested pellets; this is rarely observed, since the pellets are reingested as they are produced.[citation needed]

Hard pellets are made up of hay-like fragments of plant cuticle and stalk, being the final waste product after redigestion of soft pellets. These are only released outside the burrow and are not reingested. Soft pellets are usually produced several hours after grazing, after the hard pellets have all been excreted.[citation needed] They are made up of micro-organisms and undigested plant cell walls.[citation needed]

Rabbits are hindgut digesters. This means that most of their digestion takes place in their large intestine and cecum. In rabbits, the cecum is about 10 times bigger than the stomach and it along with the large intestine makes up roughly 40% of the rabbit's digestive tract.[12] The unique musculature of the cecum allows the intestinal tract of the rabbit to separate fibrous material from more digestible material; the fibrous material is passed as feces, while the more nutritious material is encased in a mucous lining as a cecotrope. Cecotropes, sometimes called "night feces", are high in minerals, vitamins and proteins that are necessary to the rabbit's health. Rabbits eat these to meet their nutritional requirements; the mucous coating allows the nutrients to pass through the acidic stomach for digestion in the intestines. This process allows rabbits to extract the necessary nutrients from their food.[13]

The chewed plant material collects in the large cecum, a secondary chamber between the large and small intestine containing large quantities of symbiotic bacteria that help with the digestion of cellulose and also produce certain B vitamins. The pellets are about 56% bacteria by dry weight, largely accounting for the pellets being 24.4% protein on average. The soft feces form here and contain up to five times the vitamins of hard feces. After being excreted, they are eaten whole by the rabbit and redigested in a special part of the stomach. The pellets remain intact for up to six hours in the stomach; the bacteria within continue to digest the plant carbohydrates. This double-digestion process enables rabbits to use nutrients that they may have missed during the first passage through the gut, as well as the nutrients formed by the microbial activity and thus ensures that maximum nutrition is derived from the food they eat.[9] This process serves the same purpose in the rabbit as rumination does in cattle and sheep.[14]

Rabbits are incapable of vomiting.[15] Because rabbits can't vomit, if buildup occurs within the intestines (due often to a diet with insufficient fiber[16]), intestinal blockage can occur.[17]

Sleep

Rabbits may appear to be crepuscular—most active at dawn and at dusk—but their natural inclination is toward nocturnal activity.[18] In 2011, the average sleep time of a rabbit in captivity was calculated at 8.4 hours per day.[19] As with other prey animals, rabbits often sleep with their eyes open, so that sudden movements will awaken the rabbit to respond to potential danger.[20]

Diseases

In addition to being at risk of disease from common pathogens such as Bordetella bronchiseptica and Escherichia coli, rabbits can contract the virulent, species-specific viruses RHD ("rabbit hemorrhagic hisease", a form of calicivirus)[21] or myxomatosis. Among the parasites that infect rabbits are tapeworms (such as Taenia serialis), external parasites (including fleas and mites), coccidia species, and Toxoplasma gondii.[22][23] Domesticated rabbits with a diet lacking in high fiber sources, such as hay and grass, are susceptible to potentially lethal gastrointestinal stasis.[24] Rabbits and hares are almost never found to be infected with rabies and have not been known to transmit rabies to humans.[25]

Ecology

Rabbit kits(one hour after birth)

Rabbits are prey animals and are therefore constantly aware of their surroundings. For instance, in Mediterranean Europe, rabbits are the main prey of red foxes, badgers, and Iberian lynxes.[26] If confronted by a potential threat, a rabbit may freeze and observe then warn others in the warren with powerful thumps on the ground. Rabbits have a remarkably wide field of vision, and a good deal of it is devoted to overhead scanning.[27] They survive predation by burrowing, hopping away in a zig-zag motion, and, if captured, delivering powerful kicks with their hind legs. Their strong teeth allow them to eat and to bite in order to escape a struggle.[28] The longest-lived rabbit on record, a domesticated European rabbit living in Tasmania, died at age 18.[29] The lifespan of wild rabbits is much shorter; the average longevity of an eastern cottontail, for instance, is less than one year.[30]

Environmental problems

Rabbits have been a source of environmental problems when introduced into the wild by humans. As a result of their appetites, and the rate at which they breed, feral rabbit depredation can be problematic for agriculture. Gassing, barriers (fences), shooting, snaring, and ferreting have been used to control rabbit populations, but the most effective measures are diseases such as myxomatosis (myxo or mixi, colloquially) and calicivirus. In Europe, where rabbits are farmed on a large scale, they are protected against myxomatosis and calicivirus with a genetically modified virus. The virus was developed in Spain, and is beneficial to rabbit farmers. If it were to make its way into wild populations in areas such as Australia, it could create a population boom, as those diseases are the most serious threats to rabbit survival. Rabbits in Australia and New Zealand are considered to be such a pest that land owners are legally obliged to control them.[32][33]

In some areas, wild rabbits and hares are hunted for their meat, a lean source of high quality protein.[34] In the wild, such hunting is accomplished with the aid of trained falcons, ferrets, or dogs, as well as with snares or other traps, and rifles. A caught rabbit may be dispatched with a sharp blow to the back of its head, a practice from which the term rabbit punch is derived.

Wild leporids comprise a small portion of global rabbit-meat consumption. Domesticated descendants of the European rabbit (Oryctolagus cuniculus) that are bred and kept as livestock (a practice called cuniculture) account for the estimated 200 million tons of rabbit meat produced annually.[35] In 1994, the countries with the highest consumption per capita of rabbit meat were Malta with 8.89 kilograms (19.6 lb), Italy with 5.71 kilograms (12.6 lb), and Cyprus with 4.37 kilograms (9.6 lb), falling to 0.03 kilograms (0.066 lb) in Japan. The figure for the United States was 0.14 kilograms (0.31 lb) per capita. The largest producers of rabbit meat in 1994 were China, Russia, Italy, France, and Spain.[36] Rabbit meat was once a common commodity in Sydney, Australia, but declined after the myxomatosis virus was intentionally introduced to control the exploding population of feral rabbits in the area.

In the United Kingdom, fresh rabbit is sold in butcher shops and markets, and some supermarkets sell frozen rabbit meat. At farmers markets there, including the famous Borough Market in London, rabbit carcasses are sometimes displayed hanging, unbutchered (in the traditional style), next to braces of pheasant or other small game. Rabbit meat is a feature of Moroccan cuisine, where it is cooked in a tajine with "raisins and grilled almonds added a few minutes before serving".[37] In China, rabbit meat is particularly popular in Sichuan cuisine, with its stewed rabbit, spicy diced rabbit, BBQ-style rabbit, and even spicy rabbit heads, which have been compared to spicy duck neck.[35] Rabbit meat is comparatively unpopular elsewhere in the Asia-Pacific.

An extremely rare infection associated with rabbits-as-food is tularemia (also known as rabbit fever), which may be contracted from an infected rabbit.[38] Hunters are at higher risk for tularemia because of the potential for inhaling the bacteria during the skinning process. An even more rare condition is protein poisoning, which was first noted as a consequence of eating rabbit meat to exclusion (hence the colloquial term, "rabbit starvation"). Protein poisoning, which is associated with extreme conditions of the total absence of dietary fat and protein, was noted by Vilhjalmur Stefansson in the late 19th century and in the journals of Charles Darwin.

In addition to their meat, rabbits are used for their wool, fur, and pelts, as well as their nitrogen-rich manure and their high-protein milk.[39] Production industries have developed domesticated rabbit breeds (such as the well-known Angora rabbit) to efficiently fill these needs.

In art, literature, and culture

Rabbits are often used as a symbol of fertility or rebirth, and have long been associated with spring and Easter as the Easter Bunny. The species' role as a prey animal also lends itself as a symbol of innocence, another Easter connotation. They appear in folklore and modern children's stories, often but not invariably as sympathetic characters.

In Jewish folklore, rabbits (shfanim שפנים) are associated with cowardice, a usage still current in contemporary Israeli spoken Hebrew (similar to the English colloquial use of "chicken" to denote cowardice).

WWII USAF pilot D.R. Emerson
"flys with a rabbit's foot talisman,
a gift from a New York girl friend"

Superstition and urban legend

A rabbit's foot may be carried as an amulet, believed to bring protection and good luck. This belief is found in many parts of the world, with the earliest use being recorded in Europe c. 600 BC.[42]

On the Isle of Portland in Dorset, UK, the rabbit is said to be unlucky and even speaking the creature's name can cause upset among older island residents. This is thought to date back to early times in the local quarrying industry where (to save space) extracted stones that were not fit for sale were set side in what became tall, unstable walls. The local rabbits' tendency to burrow there would weaken the walls and their collapse resulted in injuries or even death. Thus, invoking the name of the culprit became an unlucky act to be avoided. In the local culture to this day, the rabbit (when he has to be referred to) may instead be called a “long ears” or “underground mutton”, so as not to risk bringing a downfall upon oneself. While it was true 50 years ago that a pub on the island could be emptied by calling out the word "rabbit", this has become more fable than fact in modern times.[citation needed]

In other parts of Britain and in North America, invoking the rabbit's name may instead bring good luck. "Rabbit rabbit rabbit" is one variant of an apotropaic or talismanic superstition that involves saying or repeating the word "rabbit" (or "rabbits" or "white rabbits" or some combination thereof) out loud upon waking on the first day of each month, because doing so will ensure good fortune for the duration of that month.

The "rabbit test" is a term, first used in 1949, for the Friedman test, an early diagnostic tool for detecting a pregnancy in humans. It is a common misconception (or perhaps an urban legend) that the test-rabbit would die if the woman was pregnant. This led to the phrase "the rabbit died" becoming a euphemism for a positive pregnancy test.

^Karr-Lilienthal, Phd (University of Nebraska - Lincoln), Lisa (4 November 2011). "The Digestive System of the Rabbit". eXtension (a Part of the Cooperative Extension Service). Archived from the original on 6 January 2018. Retrieved 5 January 2018.